activerecord_proxy_association_bug.rb

begin
  require 'bundler/inline'
rescue LoadError => e
  $stderr.puts 'Bundler version 1.10 or later is required. Please update your Bundler'
  raise e
end

gemfile(true) do
  source 'https://rubygems.org'
  # Activate the gem you are reporting the issue against.
  gem 'activerecord', '5.0.3'
  gem 'sqlite3'
end

require 'active_record'
require 'minitest/autorun'
require 'logger'

# Ensure backward compatibility with Minitest 4
Minitest::Test = MiniTest::Unit::TestCase unless defined?(Minitest::Test)

# This connection will do for database-independent bug reports.
ActiveRecord::Base.establish_connection(adapter: 'sqlite3', database: ':memory:')
ActiveRecord::Base.logger = Logger.new(STDOUT)

ActiveRecord::Schema.define do
  create_table :articles, force: true

  create_table :comments, force: true do |t|
    t.text :content
    t.references :article, foreign_key: true
  end
end

class Article < ActiveRecord::Base
  has_many :comments do
    def build(*args, &block)
      args << { content: 'Sample' }
      super
    end
  end
end

class Comment < ActiveRecord::Base
  belongs_to :article
end

class BugTest < Minitest::Test
  def test_association_stuff
    article = Article.create!
    comment = article.comments.build

    assert_equal comment,  article.comments.first
    assert_equal 'Sample', article.comments.first.content
  end
end